Myelin basic protein (MBP) is one of the major protein components of the CNS myelin sheath. The protein is closely associated with the inner folds of the myelin membrane and is not readily accessible to the solvent. Autoimmune responses to MBP have been implicated in the demylinating diseases experimental allergic encephalomyelitis and multiple sclerosis. The role of MBP in myelin is apparently structural, providing stability to the alternating membrane bilavers. Of the 18 arginine residues in the molecule, only one (Arg-107) is methylated in a reaction with S-adenosylmethionine. The role of the methylated residue in the MBP-myelin interaction is not presently understood. We propose to isolate and purify the enzyme system responsible for the methylation reaction from oligodendroglial cell prepared from fresh bovine calf brain. Unmethylated myelin basic protein will be isolated from carp spinal cord. The fractionation of bovine MBP into methylated and unmethylated fractions will be attempted by lipid-aqueous phase paritition chromatography and by preparative isoelectric focusing. The kinetics of protein methylation will be investigated using either radioactive or continuous spectrophotometric assays coupled to adenonsine deaminase from A. oryzae. The interaction of MBP with reconstituted myelin vesicles will be investigated by monitering changes in light scattering. The role of this lipid-MPB interaction in the methyltransfer process will be investigated as will the chemical nature of this interaction. The mechanism of the enzyme-catalyzed methyl transfer will be investigated with a goal of understanding those mechanisms by which the enzyme is achieving the observed rate acceleration. Specifically these will concern the chirality of the sulfonium sulfur, isotope exchange experiments and carbene traps designed to test a mechanism involving sulfonium ylid intermediates. These studies will directly contribute to our understanding of methyl transferase enzymes, mechanisms of enzyme catalysis and the physiological consequences of the methylation of CNS myelin basic protein.